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Re: [Qemu-trivial] [Qemu-devel] [PATCH 03/12] hw/pci/pci_host.c: Avoid s


From: Stefan Weil
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH 03/12] hw/pci/pci_host.c: Avoid shifting left into sign bit
Date: Mon, 10 Mar 2014 21:03:08 +0100
User-agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.3.0

Am 10.03.2014 20:10, schrieb Peter Maydell:
> Add U suffix to avoid undefined behaviour.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  hw/pci/pci_host.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
> index 77c7d1f..2c17916 100644
> --- a/hw/pci/pci_host.c
> +++ b/hw/pci/pci_host.c
> @@ -142,8 +142,9 @@ static uint64_t pci_host_data_read(void *opaque,
>  {
>      PCIHostState *s = opaque;
>      uint32_t val;
> -    if (!(s->config_reg & (1 << 31)))
> +    if (!(s->config_reg & (1u << 31))) {
>          return 0xffffffff;

I suggest fixing that 0xffffffff, too. Do we expect here a 32 bit value
(-1) which is expanded to a 64 bit value? Then 0xffffffffffffffffULL
would be correct. Otherwise 0xffffffffU is clearer.

Michael, are 8 byte reads possible here? If yes, the current code is wrong.

> +    }
>      val = pci_data_read(s->bus, s->config_reg | (addr & 3), len);
>      PCI_DPRINTF("read addr " TARGET_FMT_plx " len %d val %x\n",
>                  addr, len, val);
> 

What about using the BIT macro from qemu/bitops.h? I think that BIT(31)
looks better than (1u << 31).

Stefan




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